I’ve got another illusion for you today. Yesterday I was walking back from Chris’ office, and as I passed through a pedestrian tunnel I saw a bike up ahead with a funny wheel. Well, at least that’s what I thought at first glance.

On second glance, though, I realized that what I was seeing was an illusion — and unlike yesterday, this one was done  naturally with mirrors.

Well, at least it occurred because of a reflective surface that acted as a mirror:

Bike seen from the tunnel, Tübingen

Looking down to the end of the tunnel in that photo, we seem to be seeing the front wheel of the bike through a window on the left.

But in fact, there’s no window there at all. Along the wall of the tunnel on the left are some pieces of glass that cover advertising posters on the wall of the tunnel. These act here like a mirror. So what we’re seeing is a reflection of the back wheel of the bike on the left almost perfectly lined up to “pose” as if it were the front wheel of the bike.

However, it’s all an illusion. Here’s a photo of what the full bike really looked like when I finally emerged from the tunnel and could see the whole scene as it really was:

The bike viewed as it really was

Note that in reality there was another bike in front of the orange bike’s front wheel.

Kind of fun. 😉